Thermally conductive silicone composition and a cured product of same

1. A silicone composition having a viscosity at 25 degrees C. of 10 to 1,000 Pa·s, and comprising (A) 100 parts by mass of an organopolysiloxane having at least two alkenyl groups per molecule and a dynamic viscosity at 25 degrees C. of 10 to 100,000 mm 2 /s, (B) an organohydrogenpolysiloxane represented by the following formula (1): wherein n and m are positive integers which meet the equations: 10≦n+m≦100 and 0.01≦n/(m+n) ≦0.3, and R 1 is, independently of each other, an alkyl group having 1 to 6 carbon atoms, (C) an organohydrogenpolysiloxane represented by the following formula (2): wherein p is a positive integer of from 5 to 1,000, and R 2 is, independently of each other, an alkyl group having 1 to 6 carbon atoms, (D) an organohydrogenpolysiloxane represented by the following formula (3): wherein k is a positive integer of from 2 to 10; R is, independently of each other, a hydrogen atom or R 4 , provided that two of R are a hydrogen atom, wherein R 4 is a group bonded to a silicon atom via a carbon atom or via a carbon atom and an oxygen atom and has a group selected from an epoxy group, an acryloyl group, a methacryloyl group, an ether group and a trialkoxysilyl group, R 3 is, independently of each other, an alkyl group having 1 to 6 carbon atoms, (E) 400 to 3,000 parts by mass of a thermally conductive filler, (F) a catalytic amount of a platinum group metal catalyst, and (G) 0.01 to 1 part by mass of a reaction retardant, wherein amounts of components (B), (C) and (D) meet the following conditions: a ratio, [the total number of Si—H groups in components (B), (C) and (D)]/[the number of alkenyl groups in component (A)], is in a range of 0.6 to 1.5; a ratio, [the total number of Si—H groups in components (C) and (D)]/[the number of Si—H groups in component (B)], is in a range of 1 to 10; and a ratio, [the number of Si—H groups in component (C)]/[the number of Si—H groups in component (D)], is in a range of 1 to 10.

2. The silicone composition according to claim 1 , wherein component (D) is an organohydrogenpolysiloxane represented by the following formula (4): wherein R 3 and R 4 are as defined above.

3. The silicone composition according to claim 1 , wherein the reaction retardant is selected from acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds.

5. The silicone composition according to claim 1 , wherein the composition further comprises an organopolysiloxane represented by the following formula (6) in an amount of 0.01 to 200 parts by mass per 100 parts by mass of component (A), wherein R 8 is, independently of each other, unsubstituted or substituted, monovalent hydrocarbon group having 1 to 18 carbon atoms; R 9 is, independently of each other, selected from alkyl, alkoxyalkyl, alkenyl and acyl groups having 1 to 5 carbon atoms; and q is an integer of from 5 to 100, and c is an integer of from 1 to 3.

6. The silicone composition according to claim 1 , wherein the composition further comprises (J) fine silica powder in an amount of 0.1 to 200 parts by mass per 100 parts by mass of component (A).

7. A semi-conductor device provided with a cured material obtained by curing the silicone composition according to claim 1 .